Method of utilizing combustion heat of the coal of low quality



April 24, 1962 KENICHI SUGA 3,031,144

METHOD OF UTILIZING COMBUSTION HEAT OF THE COAL 0F LOW QUALITY Filed Nov. 25, 1958 F THE (MEAL CF HEW QUALITY Kenichi duga, Minato-lru, Tokyo-to, Japan, assignor oi? forty percent to Nippon Shinnetsu Kogyo Kahns ltaisha, Tokyo-to, Japan, a joint-stocir company of iapan Filed Nov. 25, 1953, Ser. No. 776,312

Claims priority, application Japan Dec. 23, 1957 Claims. (Cl. 237--1l$) This invention relates to a method of utilizing cornbustion heat of the coal of low quality.

Heretofore, such coal of low quality as bone coal, lignite or brown coal can be technically and industrially roasted so far as the heat energy of said coal is about 3000 calories or more. However, in practice, combustion of the coal of which heat energy is less than about 3000 calories is very difiicult from both the technical and industrial points of view. That is to say, it is very difficult to bring the coal of said low quality to ignition temperature and a large amount of fuel is necessary. Consequently, such kind of coal as described above has not been utilized in practice although said coal is abundant natural resource.

It is, therefore, the principal object of this invention to provide an improved method of utilizing combustion heat of the coal of low quality, which does not accompany with the above-mentioned difficulties and can afford various additional advantages.

Another object of this invention is to provide an apparatus suitable for embodying said method.

Said objects and other objects of this invention have been attained by eilecting the heat exchange between a heating zone and a cooling zone by use of a fused heat carrier consisting of a material such as inorganic salt, glassy material, nonferrous metallic material, and their mixture.

in embodying this invention, two containers, one being used for coal combustion and another being used for utilization of the heat energy, are arranged in a heating chamber and each of said containers is maintained at a temperature necessary for respective purpose by a heat carrier which is packed in said heating chamber surrounding said containers.

According to the method described above, the coal, even if it is very low quality, can be easily brought to its ignition temperature resulting in eifective combustion thereof. Moreover, even when over-combustion occurs, the combustion Zone is favourably cooled by the heat carrier and the heat energy produced by over-combustion can be effectively stored in the heat carrier.

This invention will be described more fully in connection with the case, in which the container which is used for the utilization of the heat energy produced is also used for the carbonization of coal of low quality and an inorganic salt is used as the heat carrier.

That is to say, two containers each containing coal of low quality are arranged in a heating chamber containing an inorganic salt, one of said containers being used for the combustion and the other being used for the carbonization. In this apparatus, when the coal in the combustion container is ignited by a burner while feeding air or hydrogen of a suitable amount into said container, said coal burns. The thus produced combustion heat energy is absorbed by the inorganic heat carrier, thereby the temperature of said carrier rises. Thus, the heat energy absorbed in the heat carrier is transmitted to the coal in the other container, thereby said coal is subjected to carbonization resulting in production of methane and water gas which can be led out of said container into separate accumulators. The most appropriate temperatures necessary for the ignition and carbonization of the coal or" low quality can be obtained when the temperature of the heat carrier is about 500 C.700 C.

Maintenance of the heat carrier at its most appropriate temperature for maintaining both the coal containers at their active temperatures can be effectuated by calculating the caloric energy of the coal to be burnt and that of the coal to be carbonized, and by charging said coal in the amounts calculated by said calculation to balance the temperatures of said containers.

According to the above-mentioned method, the following various advantages are obtained.

(1) Combustion and carbonization of a coal of very low quality can be effectively attained within a predetermined period of time without accompaniment of nonuniform combustion. Moreover, the coke obtained by the carbonization in one container is very excellent and can be used for the production of an excellent coallite.

(2) The conventional low temperature carbonization of a coal of low quality necessitates a large amount of fuel; for example, fuel of about 200-300 kg. is necessary for obtaining one ton of the semiburnt coke from the coal of a heat energy of about 6000 calories. However, according to this invention, such fuel is not necessary, because the heat energy produced by the natural combustion of the coal of low quality is automatically transmitted to the coal to be carbonized through the heat carrier, whereby fuel charging and a measure of suppressing any over-temperature rise in the combustion zone are made unnecessary, and the combustion difiiculty is eliminated resulting in the industrial and economical combustion of the coal of very low quality.

(3) The heat energy produced by this invention can be, besides the carbonization of a coal, utilized for heating any material in solid, liquid or gaseous state by maintaining the heat carrier at a temperature above the ignition point of the coal, for instance, it can be utilized to subject charcoal, sulfuric ores, mercurous ores, calcium carbonate and the like to a dry distillation, to carry out refining distillation and decomposition of any ore, or to carry out heat decomposition of methane gas, carbon monoxide, petroleum gas, petroleum, heavy oil, natural oil and the like.

(4) The method of this invention can also be applied to the production of table salt from sea water. In this case, the distilled steam can be utilized for the generation of electric power, or can be used for the decomposition of sodium bicarbonate to obtain carbonic acid gas and soda ash. Furthermore, the method of this invention can be utilized to subject caustic soda to dehydration. As the heat carrier to be used in this invention, any organic salt such as sodium chloride, calcium chloride, barium chloride, barium fluoride, sodium carbonate, barium carbonate and the like or caustic soda, caustic potash, glass and the like, or mixtures of at least two of said substances may be used.

Nonferrous metals, such as zinc, lead, tin, aluminium alloy and the like or their mixtures may also be used as the heat carrier in this invention. Moreover, a suitable mixture of the inorganic salt, nonferrous metal and glassy material may be used as said heat carrier.

The number of the combustion container and heat utilizing container may be odd or even and any arrangement of both kinds of containers may be freely selected, for instance, they may be intermittently or continuously arranged in a heating chamber.

As described above, according to this invention, the coal of very low quality of heat energy less than about 3000 calories can be industrially utilized for the production of heat energy to be utilized for any chemical reaction, conversion, decomposition and the like by maintaining the heat carrier at a temperature between 400 C. and 700 C. which is necessary for maintaining the combustion container and heat utilizing container at their active temperatures.

The above and other novel features of this invention will be more fully understood by reference to the following examples taken in conjunction with the drawing in which the same or similar members are indicated by the same numbers and references, and in which;

FIG. 1 is a sectional elevation of an apparatus for embodying this invention.

FIG. 2 is a sectional View along the line 11-11 in FIG. 1.

PEG. 3 is a sectional elevation of another apparatus for embodying this invention.

Example 1 In FIGS. 1 and 2 is shown an example of the apparatus for embodying the method of this invention, in which a rotary kiln 2 made of a metal cylinder and a spiral-shaped or wave-shaped pipe 3 are arranged in a heating chamber 1, respectively, at its lower and upper portions, the diameter and length of said kiln being, respectively, 42.4 cm. and 363.6 cm. and the diameter and total length of said pipe being, respectively, 7.5 cm. and 2000 cm. The rotary kiln 2 and pipe 3 are, respectively, used as the combustion container and heat utilizing container, and the rotary kiln 2 is provided with longitudinal stirring plates 8 attached therein. The rotary kiln 2 is rotatably supported by bearings 11 and driven by a motor through a chain belt 18 which is hung on a chain wheel 16 attached to the kiln 2 and a chain wheel 17 attached to the shaft of the motor 15.

In the heating chamber 1 is put a mixture 4 of calcium chloride of 40%, barium chloride of 24%, sodium chloride of 16% and lithium chloride of by weight so as to surround said rotary kiln 2 and pipe 3 and then powdered coal of low quality (of about 1500 calories) is continuously charged into the rotary kiln 2 at its end opening 2a by means of a hopper 5, and air is blown into said kiln through a pipe-shaped blower 6 extending into the kiln 2 through another end opening 2b of said kiln, said blower being provided with many blow-holes 7. In the above apparatus, when the coal in the rotary kiln is ignited by a burner inserted through the end opening 2a, said coal continues its combustion. The smoke is discharged through a chamber 9 and a chimney 10 and the ash is discharged out of the end opening 2b, said chamber 9 being provided with a door 9a for the insertion of said burner. The heat produced by said combustion is transmitted to the salt mixture 4 through the wall of the rotary kiln 2, thereby the salt mixture 4 is fused at a temperature of about 370 C. and then the temperature of the fused mixture rises gradually. The rotary kiln 2 is rotated after the mixture 4 has been fused and then cooling water is circulated through the water tanks 12 which are attached to the heating chamber 1 to form ring gaps 20 between said tank and kiln, said water being charged from pipes 13 and discharged out of pipes 14, whereby the combustion of the coal in the rotary kiln is uniform and the fused mixture which overflows into the gap 20 is solidified and contracted. The fused mixture in the gap 19 acts as packing ring and the solidified mixture in the gap 20 acts as the bearing. Upon the temperature rise of the salt mixture to 630 C., steam heated to 300 C. and maintained at about 100 atmospheric pressure is charged into the pipe 3 from its opening 3a. Then, the charged steam is discharged out of another opening 31) after being heated to a temperature of about 530 C. This heated steam can be utilized for driving a steam turbine. In this example, granularity and water content of the coal particles are, respectively, selected at about 5-10 mesh and about 12%, and combustion time and combustion amount of the coal are, respectively, selected at about 18 minutes and 150 kg. per hour.

Example 2 In this example, the same apparatus as in Example 1 is I it used. In the heating chamber 1 is put a mixture 4 of alu' minum of 70% and copper of 30% by weight and then powdered coal of low quality (of about 1200 calories) is continuously charged into the rotary kiln 2 from its end opening 2a by means of a hopper 5, and air is blown into said kiln in the same manner as in Example 1. When the powdered coal in the rotary kiln is ignited, said coal continues its combustion. The heat produced by said combustion is transmitted to the metal mixture 4 surrounding said kiln. The metal mixture is fused at a temperature of about 550 C. and then the temperature of the fused mixture rises gradually. Upon the temperature rise of the metal mixture to about 600 C., water is charged into the pipe 3 from its opening 3a. Then, the charged water passes through said pipe 3 while being heated and then is discharged out of another opening 3b in the state of heated steam. The temperature of the thus discharged steam is about 170 C. when the temperature of the fused metal mixture is about 600 C. This heated steam can be utilized for the manufacture of pulp to be used for paper production. In this example, granularity and water content of the coal particles are, respectively, selected at about 5-10 mesh and about 12%, and combustion time and combustion amount are, respectively selected at about 18 minutes and 150 kg. per hour.

Exampie 3 In this example, the apparatus as shown in FIG. 3 is used, which is almost equal to that in FIG. 1 except that in this example, the combustion container consists of a stationary kiln 2 instead of the rotary kiln and the air blow pipe 6 is constructed as a screw conveyor having screw vanes 21 and air hole 22, said kiln being provided with a hopper 5 at the position near the right side end thereof and a chimney 10 at said end portion and said air blow pipe 6 is driven by a motor 15 through a chair belt 18 which is hung on a chain wheel 16 attached to said pipe 6' and a chain wheel 17 attached to the shaft of said motor 15. In the heating chamber 1 is packed a mixture of soda glass of 70%, potash glass of 20% and barium carbonate 0f 10% by weight. Powdered coal of low quality (of about 2500 calories) is continuously charged into the kiln 2 by the hopper 5 and then transferred in the arrow direction by means of the screw conveyer. On the other hand, air is charged into said kiln through the pipe 6 in the same manner as in Example 1. When the powdered coal in the kiln 2 is ignited by a burner inserted through an opening 2a of the end wall of the kiln 2, said coal continues its combustion. The heat energy produced is transmitted to the glass mixture. Thus, the glass mixture is fused at a temperature of about 720 C. and then the temperature thereof rises gradually. Upon the temperature rise of the glass mixture to about 770 C., preheated steam of about atmospheric pressure is charged into the pipe 3 from its opening 3a. Then, the charged steam passes through said pipe 3 while being heated and then is discharged out of another opening 3b in the super heated state of about 570 C. This heated steam can be utilized for driving a steam turbine. In this example, granularity and water content of the coal particles are, respectively, selected at about 8-10 mesh and about 16%, and combustion time and combustion amount are, respectively, selected at about 18 minutes and kg. per hour.

While I have described particular embodiments of my invention, it will, of course, be understood that I do not wish my invention to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What is claimed is:

1. A method of utilizing the combustion heat of coal of low quality, which comprises burning said coal in a combustion zone, directly surrounding said combustion zone with a heat-exchange body in the form of a fused solid consisting of a material selected from the group consisting of inorganic salts, glassy materials, non-ferric metals, and mixtures thereof, and passing a liquid to be heated through said body in indirect heat-exchange relationship therewith, said body being maintained at a temperature of about 500 to 700 C.

2. An apparatus for utilizing the combustion heat of coal of low quality which comprises, in combination, rotary kiln means defining a combustion zone, a casing directly surrounding at least the major portion of said rotary kiln means and containing a heat exchange body in the form of a fused solid consisting of a material selected from the group consisting of inorganic salts, glassy materials, nonferrous metals and mixtures thereof which is in direct contact with said rotary kiln means, tube means for receiving a liquid to be heated and to absorb heat from said heat exchange body immersed in said heat exchange body, said heat exchange body completely surrounding the portion of said rotary kiln means enclosed by said casing and said kiln means being provided with stirring means including an air blow pipe disposed therein, said blow pipe being provided with holes for feeding combustion air into said kiln, means for controllably introducing coal to be burned at one end of said kiln means, and means for removing coal ashes from the other end of said kiln means.

3. An apparatus as defined in claim 2, wherein said rotary kiln means has ends extending beyond said casing and said ends are provided with exterior cooling means.

4. An apparatus as defined in claim 2, wherein said tube means is in the form of a plurality of reversed curves extending longitudinally of said rotary kiln means.

5. An apparatus for utilizing the combustion heat of coal of low quality which comprises, in combination, kiln means defining a combustion zone, a casing surrounding at least the major portion of said kiln means and containing a heat-exchange body in the form of a fused solid consisting of a material selected from the group consisting of inorganic salts, glassy materials, nonferrous metals and mixtures thereof which is in direct contact with said kiln means, tube means for receiving a liquid to be heated and to absorb heat from said heat exchange body immersed in said heat-exchange body, said heat-exchange body completely surrounding the portion of said kiln means enclosed by said casing, said kiln means being provided with stirring means in the form of a screw conveyor, and said kiln means having ends extending beyond said casing with one of said ends being provided with a coal feed opening and the other of said ends being provided with an ash discharge opening, said screw conveyor being effective for controllably conveying material into said kiln means from said coal feed opening and to con vey material from said kiln means to said ash discharge opening.

References Cited in the file of this patent UNITED STATES PATENTS 1,079,151 Smallwood Nov. 18, 1913 1,340,274 Kelly May 18, 1920 1,465,277 Mayes et al. Aug. 21, 1923 2,426,348 Fulton et a1. Aug. 26, 1947 2,528,037 Crise Oct. 31, 1950 2,582,134 Kimmell et al. Jan. 8, 1952 2,592,980 Van Wert Apr. 15, 1952 2,717,580 Maher et al Sept. 13, 1955 2,791,204 Andrus May 7, 1957 FOREIGN PATENTS 263,890 Germany Sept. 29, 1913 OTHER REFERENCES Fuels and Combustion Handbook (Johnson and Auth). Published by McGraw-Hill Book Co., Inc. (New York) 1951. (Pages 374, and 375 relied on. Copy in Div. 19.) 

